<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box1 {
            width: 100px;
            height: 100px;
            background-color: red;
            position: fixed;
            left: 100px;
            top: 100px;
            }
            .box2 {
            width: 400px;
            height: 400px;
            background-color: blue;
            }
            .box3 {
            width: 100px;
            height: 100px;
            background-color: green;
            position: fixed;
            right: 30px;
            bottom: 30px;
            }
            h3{
                height: 500px;
            }
    </style>
</head>
<body>
    <div class="box1"></div>
    <div class="box2"></div>
    <div class="box3"></div>
    <h3>哈啊哈</h3>
    <h3>哈啊哈</h3>
    <h3>哈啊哈</h3>
    <h3>哈啊哈</h3>
    <h3>哈啊哈</h3>
    <h3>哈啊哈</h3>
    <h3>哈啊哈</h3>
</body>
</html>